Metallocene compounds are well known as homogeneous catalysts for polymerization of olefins. Polymerization of olefins using these metallocene compounds, particularly stereoregular polymerization of α-olefins, has improved much since the report of isotactic polymerization by W. Kaminsky et al. (Angew. Chem. Int. Ed. Engl., 24, 507 (1985)), but further improvement has been required in terms of polymerization activity and stereoregularity. As part of studies for the improvement, propylene polymerization using a metallocene compound in which a cyclopentadienyl ligand and a fluorenyl ligand are bridged, has been reported by J. A. Ewen (J. Am. Chem. Soc., 110, 6255 (1988)). Further, W. Kaminsky has reported ethylene polymerization using the same catalyst (Makromol. Chem., 193, 1643 (1992)).
However, polymerization of ethylene as a major monomer has suffered insufficient polymerization activity, so that a transition metal compound capable of enhanced polymerization activity or a polymerization catalyst comprising the transition metal compound has been demanded.